it defines marriage as "only a legal union between one man and one woman." the law had a big effect on edie windsor of new york who married tea spire in 2007. when spire died the irs sent a tax bill for $300,000 because it did not consider them to be married. >> the injustice. i couldn't believe they were making a stranger of this person i lived with and loveded for 43 something years. >> under that law, same sex couples who are legally married are denied about 1,000 federal benefits that other married couples get. after first supporting the defense of marriage act, the obama administration concluded last year that it violates the constitution. >> we cannot defend the federal government poking its nose into what states are doing and putting the thumb on the scale against same sex companies. >> reporter: house republicans are now taking up the law's legal defense. supporters say it helps preserve traditional marriage. >> unions of two men and two women are not the same thing as a marriage between a man and a woman. only marriage between a man and a woman can